The transportation of heavy cargo by truck, railway or by ships necessitates the use of reliable, safe and very strong lashing or hold-down means to prevent shifting of the cargo. Link chains are commonly employed for this purpose. Corresponding ends of cargo lashing chains of equal lengths are customarily permanently secured near one side of the cargo bed on a transport vehicle and the other chain ends are releasably secured by a variety of chain tightening devices at points near opposite sides of the cargo bed after the chains are looped over the cargo units whose heights and sizes will vary greatly.
As a consequence of cargo size variation, it is necessary to provide in each lashing chain a length adjusting and chain link locking means so that each chain before final tightening may be readily provided with a relatively large or relatively small slack loop or length adjustment loop between the cargo unit and one end of the lashing chain. The provision of such a length adjusting and locking means allows cargo lashing chains of equal lengths to be employed for practically all sizes of cargo on a railroad car, truck or the like.
It is therefore the object of the present invention to provide a chain length adjusting and locking means of the above character which is positive in its locking action and entirely safe or secure in the sense that it is impossible for the engaged and imprisoned links to become dislodged from the adjusting and locking device under any circumstances except when the two cooperating identical plate elements employed in the invention are intentionally separated by removal of their fastening means at proper times.
A further object of the invention is to provide a chain length adjuster and lock which is characterized by extreme simplicity and low manufacturing cost.
Another object is to provide in a device of the above-mentioned type means which allow the cargo lashing chain to transmit tension forces along a straight linear axis without subjecting the adjusting and locking device to twisting or bending and to impart substantially pure shearing stresses only to the removable pin means which connects the two identical plate elements of the device.
Other features and advantages of the invention will become apparent during the course of the following detailed description.
Some prior art patented devices for adjusting chains and locking them through engagement with selected chain links are shown in U.S. Pat. Nos. 1,280,163; 1,531,770; 2,387,509; 3,027,615; and 3,545,200. Generally speaking, the prior art devices in contrast to the present invention are a good deal more complex and costly, involve a greater number of parts, and do not completely eliminate the possibility, under certain circumstances, of separation of the engaged chain links from the locking or holding means. The invention is thought to be a significant improvement over all known prior art devices in terms of economy, safety and security, as well as ease of manipulation of the involved parts.